Download Chapter 18 The Immune System

Chapter 18
The Immune System
Human immunodeficiency viruses budding from a T cell
An overview of animal immune systems
Adaptive immunity
Innate immunity
The response is the same whether
or not the pathogen has been
previously encountered
External
barriers
• Skin/
exoskeleton
• Acidic
environment
• Secretions
• Mucous
membranes
• Hairs
• Cilia
Found only in
vertebrates; previous
exposure to the
pathogen enhances the
immune response
Internal
defenses
• Phagocytic cells
• NK cells
• Defensive
proteins
• Inflammatory
response
• Antibodies
• Lymphocytes
The lymphatic system
Cell mediating immune responses (1)
Cell mediating immune responses (2)
Features of selected cytokines
The inflammatory responses
An innate body defense in vertebrates caused by a release of histamine and other
chemical alarm signals that trigger increased blood flow, a local increase in white blood cells,
and fluid leakage from the blood.
The resulting inflammatory response includes redness, heat, and swelling in the affected tissues.
Pin
Skin surface
Swelling
Bacteria
Histamine
Complement system
Blood clot
Phagocytes and
fluid move
into the area
Signaling
molecules
Phagocytes
White
blood cell
Blood vessel
1
Tissue injury; signaling
molecules, such as histamine,
are released.
2
Dilation and increased leakiness of
local blood vessels; phagocytes
migrate to the area.
3
Phagocytes (macrophages and
neutrophils) consume bacteria and
cellular debris; the tissue heals.
Sequence of events in a localized innate inflammatory response
to bacteria
Some important local inflammatory mediators
polypeptides (bradykinin, kallikrein)
Macrophages contracting bacteria and preparing to engulf them
Phagocytosis and intracellular destruction of a microbe
Exocytosis
Role of phagocytosis in innate immune responses
Function of complement C3b as an opsonin
Non-specifically binding
Specifically binding
Functions of complement proteins
Role of type I interferon in preventing viral replication
endocrine
autocrine
paracrine
Anatomy of a lymph node
Derivation of B cells and T cells
Summary of the role of B, cytotoxic T, and helper T cells
in immune responses
Humoral immunity and Cellular immunity
Two types of adaptive immune responses
The humoral immune response:
makes
which bind to
B cell
Antibodies
The cell-mediated immune response:
T cell
Infected
body cell
Self-nonself complex
Antigens in
body fluid
Immunoglobin structure
Disulfide bond
-S—S-
Memory of the adaptive immune response
Clonal selection of B cells in the primary and
secondary immune response
Primary immune response
2
1 B cells with
different
antigen
receptors
Secondary immune response
Antigen
molecules
Antigen
receptor
on the cell
surface
Antibody
molecules
3 First exposure
to the antigen
Cell activation:
growth, division,
and differentiation
Antigen
molecules
Antibody
molecules
4
6 Second exposure
5
to the same antigen
First clone
Endoplasmic
reticulum
Plasma (effector) cells secreting antibodies
Second clone
Clone of plasma (effector) cells
secreting antibodies
Memory cells
Clone of memory cells
The two phases of adaptive immune response
Antibody concentration
Second exposure
to antigen X,
first exposure
to antigen Y
Secondary immune
response to
antigen X
First exposure
to antigen X
Primary immune
response to
antigen X
Primary immune
response to
antigen Y
Antibodies
to Y
Antibodies
to X
0
7
14
21
35
28
Time (days)
42
49
56
Summary of events in antibody-mediated immunity against bacteria
Primary lymphoid organs: thymus, bone marrow
Secondary lymphoid organs: spleen, lymphoid nodes
Sequence of events by which antigen is possessed and presented
to a helper T cell by macrophage or a B cell
Three events are required for the activation of helper T cells
APC
Processing and presentation of viral antigen to a cytotoxic T cell
by an infected cell
By proteasomes
The activation of a helper T cell and its role in immunity
Phagocytic cell
(yellow) engulfing
a foreign cell
Self-nonself
complex
Macrophage
Microbe
B cell
T cell
receptor
Interleukin-2
stimulates
cell division
5
3
1
2
Helper
T cell
4
6
7
Interleukin-2
activates B cells
and other T cells
Self protein
Antigen from the microbe
(nonself molecule)
Antigen-presenting
cell
Binding
site for the
self protein
Interleukin-1
stimulates the
helper T cell Binding
site for the
antigen
Humoral
immune
response
(secretion of
antibodies by
plasma cells)
Cytotoxic
T cell
Cell-mediated
immune
response
(attack on
infected cells)
How a cytotoxic T cell kills an infected cells
1
A cytotoxic T cell binds
to an infected cell.
2
Perforin makes holes in the
infected cell’s membrane,
and an enzyme that
promotes apoptosis enters.
Self-nonself
complex
Infected cell
Perforin
molecule
A hole
forming
Foreign
antigen
Cytotoxic
T cell
Enzymes that
promote
apoptosis
3
The infected cell
is destroyed.
Activation of helper T cells and cytotoxic T cells
MHC restriction of the lymphocyte receptors
Summary of events by which a bacteria infection leads to
antibody synthesis in secondary lymphoid organs
Direct enhancement of phagocytosis by antibody
Activation of classical complement pathway
by binding of antibody to bacterial antigen
Membrane attack complex
Rate of antibody production following initial exposure to an antigen
and subsequent exposure to the same antigen
Summary of events in the killing of virus-infected cells
by cytotoxic T cells
Role of IL-12 and interferon-gamma,
secreted by activated helper T cells,
in stimulating the killing ability of NK cells and macrophages
Summary of host responses to virus
Systemic responses to infection or injury
(the acute phase response)
Inhibits immune responses
Role of macrophage in immune responses
Human ABO blood groups
Major types of hypersensitivity
Immediate hypersensitivity allergic response
Mast cell
Characteristic butterfly or malar rash in a patient with
systemic lupus erythematosus
Malfunction or failure of the immune system causes disease
 Autoimmune diseases occur when the immune system turns
against the body’s own molecules.
 Examples of autoimmune diseases include
- lupus.
- rheumatoid arthritis.
- insulin-dependent diabetes mellitus.
- multiple sclerosis.
 Factors for autoimmune diseases
- Gender.
- Genetics.
- Environment.
B cell
B cell
Lupus
Rheumatoid arthritis
Tc cell
Tc cell
Multiple sclerosis
Insulin-dependent diabetes mellitus
Some possible causes of autoimmune attack
Immunodeficiency disease
 Immunodeficiency diseases occur when an immune response is
- defective.
- absent.
 SCID: severe combined immunodeficiency.
“Bubble boy”
 Immunodeficiency acquired in life.
- AIDS.
- Hodgkin’s disease (Hodgkin’s lymphoma).
 The immune system may be weakened by
- physical stress.
- emotional stress.
(Students are more likely to be sick during a week of exams)
HIV destroys helper T cells, compromising the body’s defenses
 AIDS (acquired immunodeficiency syndrome), results from
infection by HIV, the human immunodeficiency virus.
The AIDS virus usually attacks helper T cells,
impairing the
- cell-mediated immune response.
- humoral immune response.
- opening the way for
opportunistic infections.
A human helper T cell (red) under
attack by HIV (blue dots)
 AIDS patients typically die from
- opportunistic infections.
- cancers.
The rapid evolution of HIV complicates AIDS treatment
 HIV mutates very quickly.
Natural
 New strains are resistant to AIDS drugs.
 Drug-resistant strains now infect new patients.
Dr. David Da-I Ho
selection!
A “cocktail” of three separate drugs, the current treatment for people living with HIV
Allergies are overreactions to certain environmental antigens
Allergies are hypersensitive (exaggerated) responses to otherwise
harmless antigens in our surroundings.
Antigens that cause allergies are called allergens.
 Allergic reactions typically occur
- very rapidly.
- in response to tiny amounts of an allergen.
 Allergic reactions can occur in many parts of the body, including
- nasal passages.
- bronchi.
- skin.
 Symptoms of allergic reactions
- sneezing.
- runny nose.
- coughing.
- wheezing.
- itching.
The two stages of an allergic reaction
Sensitization: Initial exposure to an allergen
Later exposure to the same allergen
B cell
(plasma cell)
Mast
cell
Antigenic determinant
1 An allergen (pollen
grain) enters the
bloodstream.
Histamine
2 B cells make
antibodies.
3 Antibodies
attach to a
mast cell.
4 The allergen binds
to antibodies on
a mast cell.
5 Histamine is
released, causing
allergy symptoms.
Anaphylactic shock
An “epi pen” for counteraction of anaphylactic shock
A mini-glossary of cells and chemical mediators
involved in immune functions (1)
A mini-glossary of cells and chemical mediators
involved in immune functions (2)
A mini-glossary of cells and chemical mediators
involved in immune functions (3)